Willow charcoal is made from branches. Vine charcoal is made from twigs of grapevines. The branches and twigs are burned in a kiln without any air to produce carbonised wood. Powdered charcoal is made by grinding carbonised wood.
Willow and Vine charcoals are light and brittle. They come in different thicknesses (thin, medium, thick, and extra-thick) and hardness (extra soft, soft, medium, and hard). The different types of charcoal produce a range of tonal values from light to dark. They are ideal for sketching and outlines before painting.
There are no binders used in the making of Willow and Vine charcoals; therefore, a fixative or retouch varnish is required to fasten the charcoal to the surface to prevent smudging or lifting. The downside is that the aerosol in the spray often darkens the charcoal.
Compressed charcoal is made by mixing powdered charcoal with a wax or gum binder and then moulding the mixture into sticks. Compressed charcoal comes in different hardness and grades (e.g., 2B, 4B, 6B) that are suitable for sketching and detailed drawings. The softer sticks make intense dark markings while the harder sticks make light marking. Charcoal pencil, which is compressed charcoal encased in wood, produces fine and crisp lines. Charcoal pencils are convenient and easy to use in detailed work.
Some manufacturers tint compressed charcoal sticks and pencils with pigments to produce muted and subtle colours. The term 'White charcoal' used to refer to compressed sticks and pencils is misleading because the product contains no charcoal; it's made of chalk.